Felis felix
by Garrae
Summary: "The day Richard Castle found a stray cat strutting through an alley, uncollared, unchipped, but clearly very expensively pedigreed, was the end of his world as he knew it. He just didn't realise it. Then." Fluff in six chapters. Written for the Castle Hallowe'en Bash. Caskett Cats Universe #1
1. Chapter 1

**Chapter 1**

The day Richard Castle found a stray cat strutting through an alley, uncollared, unchipped, but clearly very expensively pedigreed, was the end of his world as he knew it. He just didn't realise it. Then.

He was quite busy enough. Being a world-class playboy, squiring beautiful women around (well, following Beckett to crime scenes: she was certainly a beautiful woman but _squiring_ might have been a bit of a linguistic stretch), writing best-selling novels and keeping a happy home was commonplace, and when he added launch parties, readings and murders to the mix, there wasn't really time for anything else. It didn't stop him wanting to add one thing more, but Beckett was as impervious to his charm as she had been since he'd apologised after the summer and she'd, begrudgingly, accepted.

He needed to take a sneaky break from the latest reading, to have a short respite from the claustrophobic crowds of fans, to rest his voice and refresh the star personality that he needed to project all evening. So he'd slipped out the back of the bookstore into a quiet, dark alley, leant against the wall, hoped he wouldn't ruin his Hugo Boss suit or worse, his hand-made shoes, and simply shut down for a few moments.

He pondered the difference between his day job, such as it was; and the ins and outs of the regimented life of the cops he followed around. Strict shifts – although they all seemed to do inordinate amounts of overtime when they had a live case – strict hierarchy. And, always at the top of the team, the stunning, sexy and still entirely unobtainable Kate Beckett.

He contemplated Beckett with a mixture of lustful enthusiasm and complete unhappiness at her lack of interest in dating him, until he noticed movement at the entrance to the alley. He peered into the gloom, barely making out the motion, until it curled around his legs, close to invisible, and on bending down he discovered it to be a pure ebony cat: not a hint of any colour; moonless, starless midnight black except for its piercing green eyes. He essayed a respectful scratch around its ears, and since it didn't scratch back, petted some more and then picked it up. It settled on to his chest and shoulder, curling into his neck. He stroked it some more, murmuring nonsense to it, and it began to purr contentedly. Castle experienced a sense of considerable pleasure that the cat liked him ( _so_ unlike Beckett), and returned the favour in spades by petting it until the purr was continuous.

Of course, right about the time he discovered that this beautiful creature was uncollared, he was also sought and summoned back to his reading: recess over. He gently put the animal down, and, ridiculously, felt the need to tell it what he was doing. He bade it farewell, but the cat followed him in, and sat, very cat-like, right at the front of the audience, to stare at him for the first few moments of the resumed reading. Then it washed a paw, and on completing its ablutions, regarded him curiously, flicked its tail dismissively and prowled proudly away. He lost sight of it immediately.

Around halfway through the second half of his reading, Castle looked up from his extract to discover Beckett, garbed in her normal, formal shirt and tailored pants, watching from the side of the room. He was rather pleased to see her. He _knew_ she was a fan.

"Beckett!" He bounced up to her, high on success and applause. "Did you enjoy it?"

Beckett quirked an eyebrow in her patented sardonic way. "I've heard worse," she drawled, and just as Castle started to pout carried on, "but I'd have been happier if I'd made the beginning of the night."

"Oooh, compliments. I knew you liked me." He stopped at her put-upon eye-roll. "Why'd you miss the beginning?"

"Busy," she said shortly.

"New case?"

"No, admin. Had some stuff to take care of."

"Oh. Never mind, you got here." He looked around, trying to spot the cat again. He didn't want it to be frightened by all the people, or worse, hurt.

"Castle, why are you looking around all the time? I know you have the attention span of a hyperactive flea, but" –

"There was this cat…"

"Cat?"

"I sneaked out back for a break," he explained, "and the cat slinked into the alley. It was gorgeous: coal black, green eyes, very elegant. It liked me."

"Something has to," Beckett snarked. Castle ignored that.

"Strange, though, it didn't have a collar. It looked far too elegant for someone not to own it."

"Maybe it was chipped," Beckett pointed out. "Less obvious, and more permanent. What did you do with it?"

"I brought it in, and it listened" –

Beckett sniggered at his fancy. "A _cat_ listened to your reading?" –

"It did. Paid more attention than most of the audience, too." He frowned at her. "But then it wandered off. I don't know where it went. I hope it's okay."

"Can't say I saw any cat when I came in," Beckett said thoughtfully. "Nope. Sorry, Castle. I'm sure it'll be on its way home by now."

Castle was disappointed by that idea, and showed it. "You think?" he asked.

"Yeah. Cats are pretty independent."

"Do you like cats?"

"Yeah, but I've never had one. We never had pets when I was young, and the job's too random to have a pet now. It wouldn't be fair."

"We never had pets either, but I've always liked cats. Plenty of cats round theatres."

"Why'd you never get one once you had the loft?"

"Alexis was small, and then Mother moved in, and she was quite enough to manage. I guess I just never thought of getting a kitten."

An enthusiastic fan wandered up at that moment. "Mr Castle, I really love your books," she gushed. "Could you autograph this one, please?"

"See you tomorrow, Castle."

"Till tomorrow," he returned automatically, and turned to the fan, who was followed by streams of others, all wanting books signed and a few personalised words so that they could say they'd met their idol. As the room began to empty, late on in the evening, Castle became aware that the cat had returned. It was perched on a chair, head over its front paws in a classical Sphinx-like position, watching him. He couldn't resist going back to it, sitting next to it, gently fondling its ears and then stroking all the way down its back. The cat purred loudly and then leapt into his lap, clearly demanding more petting.

"Okay," he stated to the cat. "I don't know who you ought to be with, but unless someone here owns you" – oddly, the cat extended its claws and growled – "how about coming home with me?" She – Castle had finally worked out that this cat was female – miaowed in approval, and climbed over his chest to pillow herself on his shoulder. Clearly she was well used to being carried around.

All the way home she stayed curled on his lap, perfectly well-behaved, not in any way bothered by the cab or the Manhattan bustle. Castle concluded that whoever's cat she had once been, she had had a very pampered life. Her fur was smooth and flawless under his stroking fingers, her eyes emerald-bright as she stared into the city night, her flexible torso slim and elegant, and even her claws were neat.

The family were long abed when Castle came home, bearing his new acquaintance.

"They'll love you," he told her. "You're beautiful."

He fussed around for a moment or two, pouring some milk into a bowl and taking it through to his study – he was always fired up to write after a reading: inspiration arriving on the high-tide of adrenaline – and making himself a mug of coffee. The quizzical look the cat gave him when he went to put the bowl on the floor made him abruptly alter his movement to place it on the desk. She jumped up after it and lapped happily, the small short movements of her tongue disposing of a reasonable quantity quite quickly. Once satisfied, she positioned herself on his desk with the grace and power of Bast, the epitome of felinity as shown in art from the earliest Egyptian hieroglyphs and frescoes. He stretched out to stroke her, completely incapable of resisting her stare.

A few minutes into both creativity and coffee, Castle noticed that the cat was watching his screen. If he hadn't known better – he was sure that cats could not learn to read – he would have sworn that she was reading his words. When he stopped, she met his confused gaze, mewed, and then padded over to his coffee mug and sniffed at it. He had the most peculiar impression that his lovely new companion liked it, but he was also sure that most cats – all cats? – didn't drink coffee. Beckett drank coffee, of course. Beckett drank enough coffee to float an aircraft carrier. He wondered why the cat reminded him of Beckett. It was probably the cool, everything-on-my-terms attitude. Come to think of it, Beckett was very feline in so many ways. Unfortunately, his chances of having Beckett curled in his lap or purring at him were approximately zero. He couldn't be sure that she wouldn't shoot him, or break his leg, if he so much as stopped her falling over. Not that she fell over, either. How she managed to balance on those heels… Anyway. The cat may have reminded him of Beckett but she wasn't Beckett. She was much more affectionate.

"I'd better find a name for you," he decided. "I can't call you she all the time, or _cat_." She miaowed, and fixed him with a hard stare. "Something appropriate. Ebony?" She didn't look impressed. It bore a remarkable resemblance to Beckett's expression every time he came up with a way-out theory. "Obsidian?" Some warmth. "I know, Onyx. A black precious stone. Okay, so you're not a stone, but your fur's gleaming just like the polished variety." She butted her head against his hand and purred. "Onyx it shall be, then." Obedient to her clear desire, he stroked her head and back, and then she jumped for his shoulder.

With a little experimentation, Castle discovered that he could type despite Onyx being attached to his shoulder, and did so, encouraged by the gentle purring vibrating against his neck. She was delightfully soft and warm, and since he had been short of any other form of soft, warm, female companionship for some time – ever since he'd really got into the Twelfth – he lavished petting on her. The next day, he decided, he'd take her to the vet and make sure she had had all her shots. Then reality descended. Before he could do that, he really ought to make sure she hadn't been reported missing. He wasn't a thief. The vet would know if she had a chip, though. The thought that she might be somebody else's pet, and that therefore he might have to give her back, made him gloomy, and inspiration began to fade.

"C'mon, Onyx. It's bedtime. Tomorrow, we'd better get you checked over. If you are someone's, they'll be missing you." He watched her prowl across the floor to his bed. "If you're not, then you can stay here." She leapt on to the bed, looking around the room. He had that same odd feeling of familiarity, and pinned it to the way Beckett looked around a crime scene: how she assessed every inch of the site and the corpse. Under the pressure of the cat's stare he shut the bathroom door and conducted his night-time ablutions in privacy. When he returned, the cat appeared to assess every inch of him, then betook herself to the bathroom, much to Castle's astonishment, butted the door almost closed, and a few moments later returned.

"You use the bathroom?" He resolved to get a litter box. _If_ he was allowed to keep this beautiful cat. "Wow." She regarded him with a _don't be dumb_ glare that, if it had only included an eye-roll, would have been exactly the same as the one Beckett bestowed on him a dozen times daily. His mind skittered off as he snuggled down. "I should introduce you to Beckett." The cat looked questioningly at him. "She's my partner. Well, she pretends she isn't, but she is. We solve murders together, and even though she growls at me and rolls her eyes she listens. She'd like you. She's beautiful, too." Onyx purred softly. "She said she liked cats. The only thing is, that the pair of you together would terrify everyone. For a cat and a human, you share a lot of the same expressions." She made a noise of disbelieving disgust. "Okay, everyone knows that cats are infinitely superior to humans." The purr returned.

Onyx curled herself up on the opposite pillow while Castle tucked himself in comfortably. Once he was installed, she placed herself neatly within the junction of his neck and shoulder, and closed her eyes. Castle emitted a contented little noise, and shortly fell into sleep. Strangely, all his dreams were of Beckett. Not that that was in any way unusual: he dreamt of Beckett most nights, but these dreams were less X-rated and more affectionate: he dreamed that she was tucked into his arms, the scent of her hair in his nostrils.

When he woke, Onyx was missing. The only evidence that she had been there was a dent in the pillow and two or three coal-black hairs. He was bitterly disappointed.

"I don't understand where she could have gone," he complained to Beckett. "She couldn't have got out."

"Sure you didn't just imagine it? You imagine everything else."

"No. I have the cat hair to prove it." Castle was determined. "I'm going to check if there are any missing cats. She was so distinctive – if she was lost, it would have been reported."

"Go ahead. I'll just get on with the trivial stuff like solving murders. Maybe Ryan'll put out an APB for you."

"You mock me," he grumped. "At least Onyx liked me. She even slept on my bed."

"Did she? You must have some good qualities, then. To a cat."

"I'm sure you'd appreciate my good qualities in bed, Detective." Beckett made a noise of disbelieving disgust. "Onyx sounded like that too. You should definitely meet her."

"Meet her? Are you seriously suggesting that I should be formally introduced to a _cat_?"

"Yep," Castle said happily. "You'd get on like a house on fire. Of course, you'd need to be nicer to me. Onyx likes me. She might not take it well if you threatened me."

Beckett looked at him with a familiar mixture of irritation and confusion. "Or we might gang up on you. Which would make far more sense. Anyway, since you can't find this mysterious cat, how about you let me get on with the day job?"

"I'll find her," Castle promised. "She was beautifully pettable and affectionate. She can have a home with me." He smirked evilly. "Of course, it would mean you'd need to share me."

"I wasn't aware I wanted to have any of you."

Castle gave her a scorching look from toes to head, lingering on her form. "Really?" he husked. Beckett acquired a line of high colour along her sharp cheekbones. "Anyway. I'm going to find Onyx and if she doesn't have an owner I'll keep her."

"Knock yourself out, Castle."

Castle spent the rest of the morning making a series of enquiries and, just in case Onyx showed up again, talking to a vet he knew who would give him a late-night appointment. He put the phone down and sighed.

"No luck?" Beckett asked, almost sympathetically.

"Nope. No-one's reported a pure black Siamese missing, but no-one's found one either."

"You're really upset," she said, surprised.

"Yeah. She was gorgeous."

"I didn't realise you were so enamoured already."

"Yeah," Castle admitted. "I guess I fell in love with her straight away."

Beckett raised an eyebrow. "I thought you only fell in lust straight away."

Castle failed to reply for a minute. Running through his head was _I fell in love with you, didn't I_? Not that that had been straight away. It had taken at least two months, right about the point he had first saved her life. But if he couldn't have Beckett, he could at least have Onyx, who was proving to be affectionate and lovable. He would have rather had both, but Beckett seemed to be as unattainable as ever.

"I can't explain it," he eventually said. Beckett didn't press him. She was, in fact, looking rather confused, which swiftly changed to sympathy.

"Why don't you get yourself a coffee and then concentrate on this nice messy murder for a while," she suggested. "Then you can go home and see if your cat turns up. She's probably sleeping in your linen closet by now, on the towels."

"Hope so," he said miserably.

"I'm sure she will. Better get some treats for her, though. That'll coax her out of her hiding place."

"Mm." He made an effort to cheer up. "What sort of treats would coax you out, Beckett? Wine? Chocolate?"

She rolled her eyes. "Bribing a cop is an offence."

"Who said anything about bribery? I'm not asking for illegal favours in return." His smile was salacious. "Just trying to make sure that when you come and meet my cat you'll be satisfied with every aspect of the evening."

She groaned, and then turned to her work. Castle continued to search through missing cat stories, becoming more unhappy with every tale of traffic accidents or fatal encounters with stray dogs. He eventually took his moping self home, but on the way stopped off to purchase a large packet of top-quality cat treats. It might work, he supposed, but a full scale search of the loft failed to find a single hint of felinity.

Around seven p.m. the doorman calls up. "Mr Castle, you know you said if I spotted a black cat…?"

"You found her?"

"Sure. She was sitting right here on the doorstep, so I let her in."

He practically ran to the elevator.

"Onyx, you naughty cat. Where'd you go off to? I was worried about you." He hoisted her on to her already-accustomed place on his shoulder and she purred into his ear as she settled. "I looked all over for you. I still don't get how you got out."

He took her upstairs and fed her a small handful of treats, watching as she neatly nibbled at them and drank some water. He'd done a little more research, and found that too much milk was bad for her stomach.

"Now, let's take you to the vet," he said. "I need to know if you're chipped or not."

From the look Onyx gave him, she didn't want to go to the vet. However, she consented to be picked up and snuggled against him, and didn't complain when he hailed a cab.

* * *

 _Thank you to readers and reviewers._

 _This is gentle, silly fluff in six chapters, for the Halloween Bash. Posting daily, as it's complete._

 _Inspiration came from InkyCoffee's cat, which featured in the CastleFicStreamCon - check it out on Twitter/Tumblr or via Griever11, to whom all thanks are due._

 _For those of you of a Beckett-ly cynical nature, I had a friend some years ago whose two Siamese cats did indeed use a normal human toilet._

 _For those of you reading What's in a Name, I really, really appreciate all your support. Although my eye is recovering well, Name is complicated (as if you all didn't know that!) and requires a lot of cross-referencing/checking back, which I am currently finding very difficult as I can't put it side by side (too small). I certainly haven't forgotten it, and indeed I have been able to continue it, but until I'm happy that I can proof read it properly I can't inflict it upon you. Maybe this will make up for the lack._


	2. Chapter 2

**Chapter 2.**

"So I found her at last night's reading," he told the vet, "and took her home." He drooped. "But I guess she must belong to someone, because she's clearly expensive and pedigreed."

"You got that right," the vet said. "You don't often see a cat like this wandering around. Let's have a look."

The vet explored carefully, during which time Onyx regarded both the vet and Castle with a dangerous glare indicating her lack of enthusiasm for the process. Castle felt that same odd sense of resemblance to Beckett's lack of enthusiasm for paperwork, and grinned rather bleakly at himself. He was clearly going insane through lack of Beckett, and therefore anthropomorphising wildly. However, Onyx, unlike Beckett, hadn't threatened or maimed him, which he considered a major advantage. She also liked him petting her, and was prepared to spend considerable time snuggled into him. Beckett would kill him just for the thought of petting her, which was deeply unfair.

"Well, Rick, she's not chipped."

Castle's jaw dropped. "She's not?"

"No. No sign that she's ever been chipped, and weirdly there's no sign that she's ever had a collar either. I can't believe she didn't have an owner – you were right, she's a pure-breed, and she'd be very expensive – but they've been really lax about her safety. Where did you say you found her?"

"The alley behind the Rizzoli Bookstore."

"Hm. Not where I'd expect a cat like that to be."

"I couldn't find any reports of one being lost."

"Weird," the vet said again. "You'd think they'd practically have an APB out. Pure black Siamese cats are rare. In fact, this is the first I've seen."

"Can I keep her?"

The vet shrugged. "You'll have to give her up if her owner proves she's theirs."

"How are they going to do that? No chip, no collar, nothing." Castle didn't know why he was so desperate to keep this cat, but he was. He had a suspicion it was because he couldn't have Beckett, and the cat's cool, sardonic look was the next best thing. "Look, Casey, if I keep her for now, how do I keep her safe? She got out last night – no idea how, I'd swear the loft was locked up, but she did, and I don't wanna lose her."

"Well, you could put a collar on her, but that's not exactly safe, 'cause all you need to do is take it off."

Onyx stretched and extended her claws in full. Castle glanced at her worriedly. "You know, it really sounded as if she understood that. I don't think she'd like a collar."

"We don't normally recommend them. It's too easy for them to catch on something." Casey turned to his kit, and held up a small chip. "Give me a moment." He fiddled about on the work surface, and turned back. "Keep her still?" Castle stroked her till she relaxed and purred at him, and then Casey swiftly pinched the skin between her shoulder-blades and injected the chip. Onyx growled fearsomely, and swatted at him, claws fully extended.

"C'mon, Onyx. That's not kind. It's just to keep you safe." Onyx growled again, spat viciously, and acquired an air of sulking. When Castle tried to pet her, she hissed and extended claws.

"We should give her the standard shots, too. You don't want her getting sick." The cat hissed very angrily. "They all do that."

Castle squatted down to be on eye level with Onyx's flat-eyed, vicious glare. "You don't wanna be sick, do you?" She hissed again. "You'd be miserable, and we'd have to come back here for treatment." She yowled. "You're as bad as Beckett, you know that? I have got to get you two together. She complains just as loudly about medics. How she manages to be friends with Lanie I don't know. Anyway, you need these shots, so lie still and when we're done we can go home."

He remembered saying the same sort of thing to Beckett, after a bruising encounter with a lowlife. She'd complained loud and long about how ridiculous it was that she should be checked over. He'd bought her coffee, after, to cheer her up.

"At least you don't need coffee to cheer you up." Onyx hissed again, but it sounded resigned. "You can have a treat when we get home." He patted her gently, but she didn't arch into his hand, to his disappointment. "It'll only take a minute or two." He turned to Casey, who was watching with some amusement. "Let's do this."

"You were talking to that cat as if she understood every word."

"Yeah, well," Castle muttered, embarrassed. "C'mon. I wanna take her home."

Casey administered the shots efficiently, and as soon as they were completed Castle picked Onyx up to fuss over and pet her until her stiff back and rigid tail relaxed. He supposed that that meant he was forgiven. "There, there," he soothed, "all done. No more needles." She hissed half-heartedly into his ear. He became very conscious of her sharp white teeth and the proximity of her claws to his earlobe.

Casey paid, they returned home.

"Dad, what have you got there?"

"This is Onyx."

"Why have you got a cat, Richard?"

"I found her."

"In a handbag?" his mother quipped.

Castle scowled. "No. In an alley. She doesn't seem to have an owner so I'm keeping her."

His mother made a disgruntled noise. "Are you sure you're not projecting your lack of female company? Really, darling, would it not be easier simply to ask Katherine on a date?"

Castle adjusted the cat to be more comfortably distributed over his chest. "Onyx is a lot more friendly than Beckett." A claw touched the skin of his back. "Anyway, I got her chipped and her shots. So can you be careful to keep the outer door shut? I'd hate to lose her."

"She's gorgeous," Alexis noted. "Can I stroke her?"

"If she doesn't object."

Onyx dropped to the ground and stalked to the middle of the living room. Alexis waited patiently, until Onyx's detailed assessment came to an end. The cat jumped on to the couch, padded along and lay down next to Alexis, who tentatively patted her. Her tail flicked restlessly, and after a few moments she vacated the couch and smoothly entered the study.

"Guess she's a one-writer cat."

The evening progressed very much like the previous night. Castle wrote, Onyx snuggled in his lap or on his chest. Late on, he put a drop or two of his coffee in a saucer for her, which she sniffed curiously and tasted. Her green eyes gave him no clue at all whether she liked it, but there didn't seem to be any left. At bedtime, she curled up just as before, though he spent some time petting her.

"Tomorrow, I'll invite Beckett round, so you can meet her. I wish she'd come round anyway, but she never drops by. I don't think she's still angry with me from the summer – she let me back." Onyx observed him with a quizzical expression. "I did something really dumb, and it upset her. I didn't mean to, but it did. So I said sorry, but I don't know if that's enough."

Onyx purred, and butted her head into his hand. "You think it is? I wish I knew. I only wanted to help her. I never wanted her to be so upset. I thought she'd never speak to me again." Another butt, and Castle cuddled his cat against his chest. "I thought I'd never see her again. Still, she let me back. Gave me another chance. If only she'd see…" He gazed down at Onyx, who gazed back. "Wish it was as easy as finding you." She mewed at him. "Yeah, I guess. You found me." He wriggled down. "Night. Till tomorrow, gorgeous." She tucked herself into his neck. That night, his hand settled on her soft fur and stroked until sleep overtook him.

In the morning, the cat was gone again. Castle performed a search of the obvious areas, but didn't spot her anywhere. He left water and cat food, hastily purchased at the store down the road, in his study, and made his way to the precinct to see if there was anything interesting going on.

"Morning, Beckett."

"Hey." She looked tired, and there were circles under her eyes.

"You okay?"

"I don't feel so good." She shifted uncomfortably, and rubbed at a spot on her back.

"What's wrong?"

"No idea. Feels like something bit me."

"Your boyfriends should take more care," Castle said mischievously.

Beckett growled angrily. "That's inappropriate," she hissed at him.

"Yeah, biting the back is definitely inappropriate – and misplaced. Nibbling earlobes, now, or" –

"Shut up, Castle."

"I could show you the appropriate way to nibble."

"No thanks. The only thing I should be nibbling is a doughnut."

"Doughnut? I don't see any doughnuts."

"That's because you haven't bought them yet."

"Why didn't you just say you wanted a doughnut?"

Beckett flexed her back again and winced. "I just did."

"You should get that bite seen to, if it hurts that much."

"Yeah. Must have been a spider."

Castle squirmed uncomfortably at the thought. "Or I could kiss it better. I could come round tonight and" –

"No."

"Humph. You're no fun. Just as well Onyx came back."

"The cat? Is that what you've called it?"

"Yes, the cat. I told you her name yesterday. You remember everything, Beckett. I know you remember my cat."

"Your cat?" There was definite emphasis on the _your_.

"Yep," Castle stated firmly. "My cat. Chipped and everything. I even got her all her shots. She didn't like it much, though. She growled and hissed at me. She sounded a lot like you on a bad day." Beckett produced a glare that would level armies. "Anyway, she's mine now. I'm not taking the chance someone else steals her."

"Next thing I know you'll be showing me photos. Have you met her parents yet? You sound like you're about to propose."

Castle ignored the snark, and fixated on the photos.

"Great idea! I'll take some tonight. Or you could drop by and meet her?"

"Busy tonight. Show me a photo. I gotta see this cat that's wormed its way into your life in two days flat."

"You'll love her. She's gorgeous. Pure black with green eyes." He cast Beckett a mischievous look. "If you were a cat, you'd have those same eyes."

"Okay, now you've lost it. I am a human. You have acquired a cat. Do not confuse us. Anthropomorphism or personification is not attractive."

"You're so _hot_ when you use polysyllables" –

"Stop right there."

Castle rapidly concluded that a doughnut trip was indicated, and took it, returning with a large box which, as ever in the bullpen, lasted a total of thirty seconds. Her doughnut didn't sweeten Beckett's temper much, but he reckoned that her irritability had much more to do with the bite and her general malaise, which she treated with a consistently maximised dosage of Advil and a refusal to pay it any more attention than that, than with him. She was still in some discomfort and very irritable when she went home.

Castle couldn't find Onyx at all when he got home. Around eight, Edward, tonight's doorman, called up.

"Mr Castle, your cat's down here." Castle considered saying _Send her up_ , and then realised that that would be utterly ridiculous. "She's sitting at the elevator." Maybe not so ridiculous.

"Um, Edward, could you try pressing the buttons for her?"

Edward snickered. "She that clever?"

"We'll find out. Go on. If she doesn't go in I'll owe you ten."

"Okay."

Castle opened his door and waited, eyes on the hallway. A moment later the elevator doors opened and Onyx regally exited, aiming straight for his door.

"Guess you really are that clever." Castle reached down to fondle her ears. "C'mon, then. Dinner time." She mewed. "You eat far too late. You're as bad as Beckett. You'll get tummy aches if you have your dinner this late." Onyx produced a look of total disdain and stalked past him, flirted the tip of her tail towards his mother in casual greeting, and continued on to the study.

Castle discovered very quickly that the spot where Onyx had been chipped was sore – right about the point he petted her back and she spat at him.

"Okay, okay! Don't do that. It's not nice. It'll be better in a day or two. You know, Beckett was sore today too. She said she got bitten. She was cross all day with it, and didn't even appreciate the doughnuts like she usually does. Just as well I didn't touch her. She wouldn't just have spat and hissed – which isn't polite, you know – she'd have twisted my ear. It really hurts when she digs her nails in."

Onyx made a face that looked as if she was laughing at him, if cats laughed.

"Don't get any ideas," Castle warned. Onyx simply mewed at him, and then jumped into his lap, turned herself around a couple of times, and settled down. He got the distinct feeling that she was waiting for him to start writing. "I can't write without coffee." He grinned. "Do you want some too?"

Onyx was at the study door before Castle had realised she'd moved. "Wow. A cat who likes coffee. Beckett'll never believe this. Oh, I need to take a picture of you. Show her. Let's get our coffee, and then I'll brush you" – she miaowed, meaningfully – "yes, I'll avoid the sore spot – and then I'll take your picture."

Brushed and supplied with a few drops of coffee, Onyx arranged herself in a model-cat pose. Castle snapped a couple of photos, but as he was putting his phone down, she prowled over to nose at the screen. "You wanna see?" he asked, feeling utterly stupid for talking so much to an animal who couldn't even reply. He showed her the pictures, and was, ridiculously, relieved when she purred. Looking for approval from a cat was a whole new level of insanity. Still, it was nice to be approved of.

"Beckett doesn't always approve of me," he told the cat. "She mostly bubbles over with disapproval. _Bubble, bubble, toil and trouble_ ," he deliberately misquoted, to a complete lack of appreciation from Onyx. "She doesn't disapprove as much now as when I first showed up, but enough. You'd think she didn't appreciate my theories. I know I'm not a cop, but I help. We think in sync. Wow, that rhymes." Another stare of complete disinterest. "She insists on being logical and having facts, but I'm the one who comes up with theories that we can toss around." He stroked Onyx's tail, which was waving over his hand. "It's so good, ripping into cases together. I love her mind. It's as hot as the rest of her." He opened his phone again, and gazed at an illicit photo he'd snapped. Onyx stretched up on her front paws, and nudged at it, then batted a paw at it. "Anyway. Let's send her this photo of you."

Castle had expected a reply fairly quickly, but when he went to bed he still hadn't had one. "I guess she wasn't feeling well with that bite. I hope she isn't sick – but if she was, I could take her chicken soup and mop her fevered brow." Onyx, curled up on the opposite pillow, hissed. "Jealous? I wouldn't be. You're here. She isn't. No chance she will be, either." He sighed. "I don't even know how to get her to come out on a date. I've given up asking." The cat tucked herself into her favourite spot. "Every so often I think she's interested and then someone interrupts or there's a murder or the moment's lost some other way." He sighed again, deeply. "I just wish I knew what she liked: movies or theatre or even grand opera. I'd even listen to Country and Western music, and I hate that. Just _something_ to break the ice."

Onyx purred, which Castle chose to interpret as sympathy. "But I've got you," he said, and patted her. Her soft tail trailed over his cheek. "You're just as gorgeous." He paused. "I wish I knew where you were hiding, though. I'm sure you can't get out, but you're hiding so cleverly you might as well be." He thought for a second. "I should get a cat flap put in, tuned to your chip. That way you could come and go as you please." The cat emitted a definitive, approving miaow. "Okay, we'll do that." He scrunched his cheek into his pillow. "Goodnight, Onyx."

He half-expected that she'd be gone in the morning, and she was. The slight feeling of disappointment was alleviated when he remembered that she had turned up each evening. He arrived in the bullpen bearing coffee and bear claws, and greeted Beckett with enthusiasm.

"Did you like the photo?"

"Uh?"

"Last night. I sent you a photo of Onyx. My cat," he pointed out, in case she'd forgotten. "You didn't reply."

"Oh, right. I didn't realise my phone was out of power till I got in. Must have been the bug I had yesterday. I went to bed early."

"I'd have made you chicken soup."

"And mopped my fevered brow? I think not."

Castle blinked. Beckett had repeated his phrase. He shook his head. That was a common expression.

"I'm fine now. Just one of those twenty-four hour things." She smiled at him, without any of the usual sardonic edges. "It was a nice thought. Now, show me this photo? My phone's still charging so let's see yours."

Castle opened the photos and displayed them with pride. "Isn't she lovely?"

"Mm. Very elegant. Not what I thought you'd like."

"Oh?"

"I'd have expected you to have a Maine Coon. Or a dog."

"No. I like Onyx. She's perfect."

Beckett twitched her lips and quirked an eyebrow quizzically. "Perfect?"

"Gorgeous, affectionate, pettable…" He frowned. "I just wish she didn't disappear all day. I worry about her, even if she does come back at night."

"Cats are pretty independent."

"Yeah. Oh, I'd better get on to the handyman. I need them to install a cat flap. One of those hi-tech ones that only opens to let her in when it senses the microchip."

"Won't that mean she can get out?"

"No. I researched it. There are one way types."

"Sounds like a plan," Beckett noted idly. Her attention had already shifted to her case file.

A short call later, Castle made his apologies and left to meet the handyman. He returned in the afternoon, exuding satisfaction.

"All done. She can come in as she pleases. So, why don't you come round for dinner and maybe she'll show up?"

Castle felt very nervous about asking Beckett over, but she hadn't said _no_ yet and she wasn't torturing him.

"Okay," she agreed, to his surprise. "Can we make it early, though? I'm still a bit sore from that bite, and I don't want to be out late."

"Sure. Six?"

"Okay." She favoured him with another un-sardonic smile. "Thanks."

* * *

 _Thank you to all readers, reviewers, and those who follow and favourite. Much appreciated, especially guests._

 _Hawkie (guest) - thank you. Still accented, after all this time._


	3. Chapter 3

**Chapter 3.**

Castle settled on a baked chicken dish with spinach and roast parsnips, making it while hoping that Onyx would show up. He had kept the chicken trimmings, carefully checked to ensure there were no flakes of bone, for her. However, when Beckett rang the doorbell there had been no sign of his lovely cat.

Beckett had obviously been home to change, and was elegantly casual in a pale silk tee and form-fitting black jeans. She produced a bottle of wine, at the name of which Castle raised his brows.

"Nice. Thanks."

"I thought you'd like it."

"Shall we try it, while dinner's cooking?"

"Okay."

Beckett settled herself on the couch, sipping at her wine. "It is good."

Castle sat down next to her. "Yeah," he agreed. "Where'd you get it?"

"Liquor store on my block. It was the last bottle."

"It's really good."

"Says the oenophile."

Castle showed his admiration in a low whistle and wide smile. "I love your vocabulary," he said.

Beckett smirked smugly.

"What do you do when you're not at work?" he asked, out of the blue. Anything to keep a civil conversation going, and _not_ ask something entirely inappropriate, such as _can I stroke you?_ or _can I kiss you?_ or simply _be mine_?

Beckett blinked, surprised. "Yoga classes." She paused to think. "I sometimes go to a Russian conversation class to keep that current, but only if I've time. You know I run."

"Yeah. Didn't know about the yoga, though, or the Russian classes – is that how you managed it with the poker ring?" She nodded, agreeing. "D'you ever go to movies, or the theatre?"

"Sometimes." She swallowed another mouthful of wine, and smiled. "But it's no fun on my own, and Lanie's schedule is as bad as mine. Anyway, she doesn't like action movies, or sci-fi, and I can only stand one rom-com every half year."

"You like sci-fi?"

"Yep. Forbidden Planet is the best movie ever."

"I've seen it about a million times," Castle told her. "It's great. I like John Woo, too."

"You do? I love his movies."

The discussion rapidly encompassed an in-depth analysis of every John Woo movie ever made. Beckett could have answered quiz questions on the subject, and Castle wasn't behind in his knowledge. Conversation was only interrupted by the beep of the oven, and resumed immediately they had companionably set everything out.

"What about music?"

"Most things. Not grand opera – ugh. Fat, screeching Italians dying over fifteen minutes and a dozen arias. Every time you think it's over they resurrect for another repetition. Ugh," she added firmly. "And I _loathe_ Country and Western. The tunes are sometimes good, but then you listen to the words."

"Not impressed by _Stand By Your Man_?"

"Hell no. Outdated, sexist rubbish."

Castle mused that it was just as well that he was the very model of a modern metrosexual, and then had an idea.

"Do you like Gilbert and Sullivan?"

"Huh? Where'd that come from? Yes, if it's done well. If the diction's sloppy it's awful."

"There's a show on. _The Pirates of Penzance_. It's not quite Broadway standard, but certainly not one of my mother's off-off-off-Broadway specials. Wanna go? I could get good tickets for us."

Beckett appeared to be quite shocked at the suggestion. "Really?"

"C'mon. It'll be fun. I'm not taking Mother – she'll critique everything all the way through and won't shut up – and Alexis doesn't get the references yet and doesn't like it. She'd rather listen to Taylor Swift with her friends."

"Okay," Beckett assented rather weakly, and immediately took a mouthful of chicken to shore herself up.

"I'll book them straight after dinner."

"Okay."

Dinner finished and cleared, Castle made them good coffee and took it over to the couch. Perforce, Beckett sat down, kicking off her shoes, and then curled herself up in the corner with her toes tucked under her.

"Onyx does that," Castle said ingenuously. "I wonder where she's got to? She should be home by now."

"She's not a child, she's a cat. She'll come when she's ready." Castle's eyes crinkled in a very wicked way. "Don't say it."

"Say what?"

"Whatever you were thinking."

"Take your mind out the gutter, Detective. My thoughts are entirely pure."

"Purely wicked."

"I'm hurt," Castle pouted. "And after I invited you to the theatre, too. Uh. I'd better fix that before all the good seats go." He stood up and went to retrieve his laptop. "Here we are. Two, centre circle. Best views." He clicked rapidly. "Done."

"How much" –

"No, no. My treat. You can treat me another time." He plastered on a fake scowl, which lasted all of ten seconds, and very carefully avoided saying _I'm paying for our first date_.

"Okay. As long as you don't want to go to a Country and Western gig."

"I think I got that you don't like that," Castle said dryly. "No. I don't like it much either."

Somehow, Beckett's elegantly folded legs had gravitated to be adjacent to Castle's thigh, which did nothing for his coolness or calm. She was peeking over her coffee cup, which was amazingly cute and very, very arousing. He hadn't even tried to put an arm round her, but kissing her had been at the front of his mind from the moment she'd agreed to come to dinner.

She drained her cup, and looked down at her watch. "It's after eight," she said. Castle thought – hoped – he detected a slight note of disappointment in her voice. "I've got to get home. I'm still a bit tired after that bite."

Castle walked to the door with her, and was just reaching for the handle when he realised that Beckett in ballet flats was at the perfect height for hugging. Not being one to stifle his impulses, he did just that. She jumped, and then wriggled.

"Ow."

"Sorry, sorry. Did I get your bite?"

"Yeah. Ouch." She undertook a complicated looking squirm and stretch. "Night, Castle. Thanks for dinner." She flicked her glance away from his lips. "I really enjoyed it. Sorry I didn't get to meet the cat, though."

"Another time. Till tomorrow, Beckett."

He heard the ting of the elevator and sat back down in his study, pulling the laptop to him and enclosed in a soft cloud of happiness. Beckett came round, had dinner, and agreed to go on a _date_ (even if he hadn't exactly said _date_ ) and he's found out a bit about what she likes. It's just a shame that Onyx hadn't come home.

"There you are!" he said, a mere moment later, as Onyx strutted through the door. "You missed Beckett." Onyx made her disinterest plain. "You'd like her. You'd better like her, because she'll come round a lot more if I can manage it." He petted her gently, very lightly running his fingers over the spot on her back where the shots had been given. She didn't spit and hiss that time, though she was definitely tense. He concluded that there was still some discomfort there. "Getting better." His fingers worked over all the points that seemed to please his elegant feline the most, until she purred at him and wound herself around his hands, ending up, already unsurprisingly, snuggled into his lap where she watched the screen change as he typed. She behaved as if she could read it, miaowing if he paused, almost huffing when he had to take a break.

"You're a fan," he said softly, and fondled her ears. "Don't go giving anyone spoilers. Gina'd never forgive me. _Beckett_ would never forgive me. She's a fan, but she doesn't know I know that. She's read all my books, even the first ones. _I_ wouldn't read the first ones. They're pretty poor."

Onyx flicked her tail in agreement with him. "Everyone's a critic, even you," Castle said comfortably. "Fortunately the book-buying public isn't so picky. Anyway, you're not to give the plot away to Beckett, you hear me? She'd be cross if you did. I've just had a lovely evening with her, even if I didn't get to kiss her, _and_ she's coming to the theatre with me, _and_ she said next time it would be her treat." He picked up the cat and settled her on to his chest, putting up with her tail tickling his chin. "Maybe next time I'll manage a goodnight kiss. As long as her back isn't hurting. Yours isn't so bad any more. I've wanted to kiss her for so long. Since I first saw her. She was amazing. I didn't realise, for a while, but she's only got more extraordinary with time. I dedicated the first Nikki book to her because of that, but I don't think she realises how much I meant it."

He stroked Onyx. "Maybe now she's coming to the theatre we could see if there's more to it," he said hopefully. "I think there is. I really wanna find out." Onyx purred softly, warm against him. "Maybe," he continued softly, and trailed off. "C'mon, beautiful. It's bedtime."

Onyx hit the bathroom first. Castle remembered that he hadn't ever bought a litter box, but Onyx seemed to have been toilet trained, quite literally. He shrugged. It certainly made life easier, though being beaten to the bathroom by his cat was a tad disconcerting. She emerged, radiating feline satisfaction, and sat primly on a pillow to watch him strip down to his boxers. Castle was well used to being watched as he undressed, and when it was a pretty woman was not shy of reciprocating or playing to the gallery. His cat's focused regard, however, was deeply strange. She hadn't done that on previous evenings. He put it down to her relatively late return, attended to his own night-time routine, and slid into bed to the accompaniment of gentle purring and the already-familiar feeling of soft fur against his skin.

"If you waited around till I got up, you could visit the Twelfth with me. They'd all like you," he told her sleepily. "We could do with another pair of eyes, sometimes." He yawned. "Night."

Naturally, his contrary cat wasn't there in the morning to be taken to the Twelfth. Equally naturally, Beckett was in the bullpen, and from the detritus of coffee cups around her, had been there for some time.

"We caught a break," she told him. "I'm just waiting for the warrant. If you hadn't shown up, I'd have called you. The probable perp is holed up in a warehouse on the docks. Ryan and Espo are already on the way there, but I can't give the go till I get the damn – yes! Here it is." She pulled out her phone and alerted the boys, telling them to stay put till they got there. "Don't forget your vest. This could be messy."

It was raining by the time they got to the docks. After a hurried strategic discussion, Esposito kicked the door in and Beckett took point, the boys fanning out behind her. The warehouse wasn't well lit, and each nook and cranny was in deep shadow, with plenty of places for people to hide. There were small sounds of movement around them: could have been the bad guy, could have been rats. Beckett signalled them to spread out: she took left, Espo straight on, Ryan to the right. Castle stayed back: a lesson he'd painfully learned during the voodoo case and hadn't forgotten since. He had learned that trying to protect Beckett actually placed her in more danger, because he didn't carry and if he had done, and then shot someone, he would be at the centre of a very messy situation. So he stayed in a sensible place: quietly, warily following; phone silenced (another never again error).

Then it all went to hell in half a minute. Beckett yelled, Esposito fired, Ryan shouted – and suddenly there were _four_ guys, big bruiser types: two of them already on Beckett, who'd not got her gun round in time and whose defensive drills weren't enough to take down two heavyweights though she landed some gut-rocking kicks and those heels had to hurt them; Espo despatching his thug in a matter of a moment or so but still a crucial few feet away; Castle trying to weigh in but succeeding only in removing one man, who managed to send a heavy-booted foot into Beckett's ribs before Castle planted a violent uppercut on his chin that felled him for long enough for Castle to knock him right out with a haymaker of a punch and turn to Beckett, who was holding a foetal position on the ground, trying – and failing – to minimise the beating she was taking. Espo dived in and took the other bruiser out just in time, because Castle had every intention of killing him. In the background, Ryan, breathing hard and painfully, had cuffed his guy and come to help.

"Beckett? Beckett, say something!"

"Oh, ow, ohhhhh," she moaned. "Fuck, I hurt."

"Can you move?"

She tried. "Owwww." Castle took a proper look at her. Her face was largely untouched, probably because her arms were over it and were already colouring livid black and blue. He was far more worried that they had broken a rib or several, or done internal damage. "Owwww."

"Beckett," Esposito knelt down by her. "Where does it hurt? Ryan's calling the bus."

"No bus."

"Yes bus. Castle'll go with you."

"Don't wanna bus. Gimme a minute."

"You need checked over. You can't even straighten out, never mind stand. I'll make the reports. We got 'em all. Me n' Ryan can handle it from here."

"Don't – owwwww, fuck." She dissolved into a small puddle of vicious profanity. Castle took her hand, and stayed with her until the ambulance arrived and she was loaded in. He followed, and sat with her, lamenting his crushed fingers with every bump or pothole. By the time they reached Bellevue, she had cursed under her breath – mostly under her breath – every inch of the way.

He sat in the waiting room until she was patched up. No broken ribs – not even a crack, which the doctors found surprising; no internal damage, which was astonishingly lucky. She was bruised from top to toe; even so, she was safe to be released. Castle made sure to escort her home, but didn't ask to go up and wasn't invited. Given Beckett's intense dislike of injury or weakness, he doubted that he'd see her for a couple of days. Esposito had already let him know that Montgomery had given her the next three days off, and then the weekend off the rota, to recover. He decided that he'd call her on the third day: see if she were recovered enough for him to take her ice-cream, or just go over and amuse her. He went home, hoping that Onyx would be there. He strongly felt the need to cuddle something, and Onyx had, astonishingly, already become his confidante.

A cat confidante? Was that what he was reduced to? Talking to his cat? But… she was there, and she couldn't tell his secrets to anyone else, and she reminded him so much of Beckett, in her sardonic, knowing stare and proud walk, even down to the tone of her mewing and that she drank coffee. Drips, of course: he was sure a cat shouldn't drink coffee in the way that Beckett mainlined it.

He called out for her, but there was no mewing, no prideful prowl or warm lapful of elegant darkness. Depressed, he entered his study, and moped industriously until his phone rang.

"Mr Castle?"

"Edward, what is it?"

"I got your cat here. She's hurt, I think. Real bad. She's crying." Castle could hear her.

"I'll be right down. Can you get a cab for me?"

"Sure thing."

Castle barrelled down to the entry hall and found Onyx curled up tight, whimpering and crying. "Did you see anything?"

"Not a thing."

"I'm taking her straight to the vet. If you find out anything…" He didn't need to finish the sentence. He picked up Onyx as gently as he could, cradling her to him and trying not to put any pressure on her. He had no idea how she could have been hurt.

"What happened?" he murmured to her. "Who did this? If I find them, I'll have them strung up."

The cab delivered them to the same vet as had chipped her.

"Casey, she's hurt. Can you give her something? Painkillers for cats?"

"Give me a second." Casey reached for a syringe and swiftly pinched the cat's skin to inject it. She gave a little feline sigh and relaxed. "She'll be better off doped. Otherwise this might hurt a bit, and we don't want that." He ran his hands over her body, then her legs, and finally her skull and ears. "Okay. Head's fine, back legs are okay, but she's pretty sore about the body and front legs. Feels like someone kicked her about."

Castle's answering growl was terrifying. "If I find who did it…"

"Yeah. I'll help."

"So what do I do for her?"

"Keep her somewhere soft. She probably won't want to move about much. Maybe a blanket, or a pillow if you've got one. If she wants petting, just do it very carefully. The anaesthetic'll wear off in a couple of hours, and she's going to be pretty unhappy for a couple of days. She's really lucky not to have more damage. She's even luckier to have you to look after her."

Casey found Castle a soft blanket to wrap Onyx in; he paid the check, and carried her out, supported in his arms. "Okay, let's get you home and tucked up. Best thing for you." She whimpered pathetically at him; in no way reaching a mew. Her limp body worried him deeply, and in the cab he was hard put to it not to rub his face into her fur, cuddle her too closely to be good for her bruising. He restrained himself, all the way home, and took her up into the loft with exquisite care, placing her on the pillow she preferred and then lifting that. She managed to emit a small, hurting purr which broke his heart all over again. He'd had too much stress today: Beckett beaten up and his beautiful cat hurt who-knows-how. (but if he finds out how, they will _suffer_ ) It had definitely _not_ been a good day: his two loves both badly hurt.

* * *

 _Thank you to all readers and reviewers, especially guests whom I can't thank directly._

 _No non-fictional cats were hurt in the writing of this fic. The same cannot be said, I'm afraid, for the lyrics of "I am the very model of a modern Major-General". A version, tailored to Castle, is being posted under the title "Modern Metrosexual" simultaneously with this chapter, where it is referenced. For those of you who appreciate Gilbert and Sullivan, I apologise._


	4. Chapter 4

**Chapter 4.**

He set Onyx, on her pillow, on his desk. He thought she looked at him gratefully as he patted her paw.

"Coffee time," he told her. "I need a drink, too. You don't get Scotch. Cats don't drink whisky." Her head descended to rest on her paws. "Just stay there and rest."

He came back with his coffee, the usual few drips for Onyx, and poured himself a small Scotch. Onyx stared coldly at the glass, and in obedience to the hard stare Castle let her sniff it. She sneezed, and then whimpered. Sneezing clearly hurt.

"See, Scotch isn't good for you. Drink your coffee, and then I'll get you some water. Whenever I take painkillers I need lots of water." She lapped slowly, under Castle's concerned eyes, and when she was finished he brought her a full bowl of water so that she might drink as she pleased. He downed his Scotch in one, appreciating the burn and warmth, and then turned to his coffee and laptop. Onyx mewed, displeasedly, the pain evident in her noise.

"What's wrong?" Castle examined her. "You want to see what I'm doing? Okay then." He rearranged himself and the laptop so that Onyx need not move, and she stopped complaining. "Silly cat. Cats don't read. Maybe you think it's electronic mice running round the screen?" He stopped talking when he realised just how insane that sounded.

"You're far too easy to talk to," he explained to the cat, who didn't look impressed by his compliment. "Not that you ever talk back. Though if you talked like Beckett you'd have spent the last three hours swearing at me, so it's just as well you don't. I never knew she knew so many bad words. Some of them even I'd never heard before, though I think they might have been in Russian. I hate it when she's hurt. She disappears off and won't see anyone. Never wants help, or coddling. God knows what she'd do if she got really badly hurt." He frowned. "I'd've looked after her, but she didn't even give me the chance." Onyx mewled softly. "Yeah, I know. I've got to look after you. I'm sure I could have managed both of you at once, though." He leaned forward, petting her skull lightly. "I don't think I want to write tonight. Too close to home. I think I'll watch a movie. It'll take my mind off it. I was really terrified that they'd done major damage to her. I hope she's taking care of herself. I wish she'd let me…"

His cat didn't say anything. Castle put on a silly, slapstick movie rather than one of his action thrillers, and settled down to watch and be comforted by the idiocy of the plot, occasionally stroking Onyx with light, barely touching strokes. She quirked her tail at him, which he decided was approval, though she wasn't purring.

When he next looked at her, her eyes were closed and her body completely limp. If he hadn't seen her ribs expanding, he'd have thought she was dead. The thought wrenched his gut, and he laid his palm very gently over her middle, only for long enough to ensure that she was warm and breathing. He finished watching the film, which had cheered him only somewhat, and picked up cat and pillow to take her into the bedroom. "Don't go running off tonight," he admonished her despite her being asleep. "You're in no state to go wandering." He missed her warm furriness at his neck as he fell into slumber.

In the morning, Onyx was still curled on her pillow, a circle of midnight in the clear light of day. Castle stumbled out of bed and through a shower and shave, during which time she didn't move so much as the tip of an ebony ear. He checked that she was breathing, shocked by how worried about her he was, and then took her, still curled on the pillow, out to the main room. Stupidly, he didn't want her to open her eyes without him being near. Over his first coffee, he tapped out a text to Beckett: _hope you're okay, please take the painkillers._ He didn't expect an answer, and didn't get one.

The day passed slowly. Onyx barely moved from her spot, although in deference to both her feline dignity and the cleanliness of his pillow Castle carried her to the bathroom a couple of times, receiving merely a mew for his trouble. He wrote desultorily, supplied the cat with water and cat food at intervals, and petted her very carefully at much shorter intervals. She took it as her due, but mostly she slept. Eventually, late that night, so did Castle.

For the second morning in a row, she was there when he woke. He looked over and saw bright green eyes staring back at him. "Well, good morning," he said to her. She emitted a miaow in return. "Feeling better?" He sat up and scrubbed at his eyes. "I need coffee. And breakfast. Lots of breakfast. I missed dinner two days in a row, I was so worried about you." Onyx stretched very slightly, and stopped. "Still sore? C'mon, then, I'll carry you." He picked up the pillow again, and saw with some amusement that she was lying on it as regally as any queen. "You know a female cat is called a queen? Guess now I know why."

He automatically checked his phone, but there was still nothing there from Beckett. He wasn't surprised, but that didn't ameliorate his disappointment. He guessed that she was too hurt to answer, or too hurt to admit in how much pain she was. He decided to send her another cheery text later.

"I wish she'd answered," he grumped to Onyx over bacon and eggs, feeding her fragments of the meat. She simply stared at him, her cat's eyes unblinking. "You don't care, do you?" Her tail twitched, and then lashed back and forth. "Are you bored too?"

He finished breakfast, and bounced up. "I know. Let's show you the precinct. Okay, Beckett's not there, but I'm not going to disturb her when she's recovering. She'll shoot me. She won't even shoot me dead, she'll shoot me somewhere painful and watch me suffer." The cat regarded him stonily. "Yeah, okay. I'd deserve it – what am I saying? I would so _not_ deserve it. Stop looking at me like that. You remind me of Beckett at her formidably intimidating best when you look like that. It's not nice. One truly intimidating woman in my life is enough. If you start doing that I'll think you're first cousin to Bagheera." The cat continued to glare, thoroughly unimpressed by his waffle. "Let's go, then. Come and meet my pals." She remained coolly indifferent.

Castle walked into the precinct with Onyx in his arms, delicately balanced to keep her from aching. He was none too sure that she wouldn't scratch or claw – or even bite – if he jarred her.

"Hey, guys," he announced. "Meet Onyx."

"You brought a _cat_ to the bullpen?" Esposito scoffed. "Man, you're insane. Whatcha do that for?"

Ryan trotted up to see what was going on. "Hey, Castle. Whatcha got there?"

Castle opened his arms a fraction to show off Onyx. "We were bored," he said.

"You came over because your cat is bored?" Espo exclaimed. "You've lost it. 'S not even 's if Beckett's here for you to moon over."

"Hey!" Castle squawked, indignantly. "I do not." Onyx added a growl.

"Gotta say, though, it looks just as unimpressed with you as she does."

Ryan sidled up close. "It's really cute," he said. She snapped at him, and he barely pulled his fingers back in time. "Wow. Bad-tempered." She growled again, claws extending.

"She's a girl," Castle said.

"She's still bad-tempered," Ryan groused.

"You're just sore 'cause she don't like you," Esposito jibed. He came closer, and allowed the cat to sniff at his calloused fingers. She didn't take umbrage, but Castle couldn't have said she exhibited any pleasure. He put her down on his chair. She turned round, assessing it, and then stepped, a little cautiously, on to the desk, examined the elephants and the computer, padded delicately across it and settled herself on Beckett's chair.

The three men regarded each other with a set of matched shrugs. "I told Beckett my chair was really uncomfortable," Castle said with an air of vindication.

"Don't think you can prove anythin' by a cat."

"Let's take a photo. Send it to Beckett," Ryan suggested. "Cheer her up. We could tell her it's her new partner." They all snickered. The cat yawned, and ignored them magnificently. Suddenly her ears twitched and pricked up, and then she sat up straight.

"What's this?" Captain Montgomery's soft, inquiring tones left Ryan and Esposito caught out, and Castle a little embarrassed.

"She's my new cat," he admitted. "She got knocked about a couple of days ago and we were bored" – Montgomery raised an utterly sceptical eyebrow – "so I thought I'd bring her in to see the precinct."

"I see," said Montgomery in a tone which indicated that he didn't see at all. "And why is this _cat_ sitting on Beckett's chair? I don't think that's going to go down well." Onyx glared at him. Montgomery didn't so much as blink.

"Beckett's not here, sir. She's got another couple of days' medical leave after the beating she took."

"We thought a photo of her new partner would cheer her up," Ryan put in, smirking.

"Hm. Don't think I agree with that," Montgomery drawled, "but it's your asses that I won't be saving when she whups them. Now, detectives, how about doing some work? You know, what the city pays you for?" They jumped to it. "Castle, pretty as your pet is, she doesn't belong here. Cats don't solve crimes, so take her home. I don't want to see her in here if Beckett's working. She'll be a distraction."

"Distraction?"

"Beckett's dead keen on cats. Dunno why. LT got a kitten and Beckett was all over the photos. Weird. Didn't think she had a sappy cell in her whole body." Montgomery slid back towards his office and Castle took the hint-cum-order to leave.

"C'mon, Onyx. Home time." He gathered her up gently, tickled her under her chin and placed her softly on his shoulder, where she scrabbled a little for balance and grip till he supported her properly. She rewarded him with a better attempt at a purr than he'd heard since she'd been hurt.

"See you, guys."

"Seeya."

Castle meandered home with Onyx, installed her in his lap, and, satisfied that she was recovering, wrote consistently until dinnertime, accompanied by occasional mews or purrs.

"I think I'll go over and check on Beckett tomorrow," he announced over dinner.

"Really, darling? Will she want to see you?"

"Probably not, but someone has to make sure she's eating and taking the painkillers." Castle rapidly changed the subject. "Did I say we were going to see _The Pirates of Penzance_ next week?"

His mother and Alexis were flabbergasted. "You what? Katherine is going to the theatre with you? Oh, darling, that's _wonderful_."

"That's great, Dad." Alexis looked truly pleased for him. "Maybe she'll see the better side of you."

"Something other than the party playboy, that's for sure, kiddo. Enjoy."

Castle finished his dinner and went back to his writing. In the interval, Onyx had picked at her dinner, but drunk most of her water. He refilled the bowl, and took the half-eaten dinner away.

"You have to eat, even if you're hurting," he told her. "You won't heal as fast if you don't." She mewed sceptically. "You have to be better by next week. I can't take you to the theatre with us. I won't take you to Beckett's tomorrow if you're not better, either."

Onyx appeared completely indifferent to the prospect of meeting Beckett. Castle dropped the subject in favour of sending the photo of Onyx on her chair to Beckett, and then writing for the rest of the evening.

That night, he dreamed of Beckett again, affectionately cuddled into his chest with her hair tickling the ends of his nose and his neck. It was certainly different from his X-rated dreams. Onyx was there when he woke, patting at him with a soft-padded paw as if to say _wake up, Castle_ , but sometime between breakfast, when she deigned to eat a reasonable amount and then delicately washed herself all over, and Castle exiting his morning shower, she'd hidden herself again. He called for her a couple of times, and then gave up. His beautiful, elegant cat would reappear when she was ready, and though he loved her curled comfortably on his lap or snuggled over his shoulder, he knew that cats were independent, walk-alone creatures, and his streak of midnight felinity had independence and pride to rival Lucifer.

"Okay," he said to the empty study. "She'll be back when she arrives." He turned to his laptop and typed industriously until he decided that it was a civilised hour to go visiting the afflicted: to wit, Beckett.

He arrived at her door with a bunch of elegantly arranged flowers, not too elaborate, and a box of chocolates. Beckett liked treats, in the form of candy, and her desk drawers were never short of an emergency supply of M&Ms or Hersheys. Just long enough after he knocked for him to start to worry, the door opened.

"Hey, Castle," she emitted tiredly.

"Hey." He stepped inside at her gesture of invitation. "I brought you these." He extended the flowers, and put the chocolates down on a convenient table. She didn't stretch to take them, but stepped forward. "Do you wanna tell me where to find a vase?" he asked, alive to the small signs of pain.

"Cupboard over the washer. Thanks."

He fetched the vase, filled it with water, and deftly arranged the flowers to best advantage. "I brought some chocolate, as well. I thought you'd like something sweet. As well as me, of course."

"Way to spoil the moment, Castle." But though she had snarked, she was smiling. "Thanks. I'll enjoy them."

"How're you feeling?"

Castle ran his eyes over her. The soft tee and sweatpants that she wore didn't conceal the livid green-and-yellow bruising on her arms, and he was quite certain that a bra had not figured in her dressing. She was very soft and unstructured.

"I'm fine." He raised eyebrows. "Okay, as fine as you can expect." She paused. "Why'd you come over?"

"Well, I couldn't let my partner suffer all on her own, so I thought I'd cheer you up. Service your every need, that sort of thing."

Beckett's eyes gleamed green. "Ri-ight," she drawled slowly. "My every need? What if I needed" – she stopped significantly – "a hit man?"

"You?" Castle said unflatteringly quickly. "Need a hit man? You'd shoot them yourself. You're as independent as my cat." His mind wandered. "I sent you a photo from the bullpen. I took her in there."

"Castle," Beckett said disbelievingly, "why on earth did you take a cat to the precinct?"

"She was bored – oh. I didn't tell you. Some bastard hurt her. She came home crying and I had to take her to the vet. It was the same day you got hurt. It really was not a good day, both my favourite women getting beaten up – er…." He stopped talking about seven words too late. Astonishingly, Beckett didn't make any moves to kill him. In fact, her jaw had dropped and her eyes were wide. He returned to the original subject while he was still more or less ahead.

"So I took her to the precinct and look," he noted, taking out his phone and flicking through the photos, "she liked your chair."

Beckett stiffly reached for the phone to examine the photo. "Huh," she breathed. "Don't think she'll be replacing me, though. How'd the boys take it?"

"She tried to bite Ryan. I don't think Onyx likes being called cute."

"I can see her point," Beckett agreed very dryly. "She's elegant. Not cute. Kittens are cute, but not full-grown cats."

"Montgomery didn't approve, though. So we went home." Castle remembered the conversation. "He said you were really keen on cats. All over LT's kitten pictures."

"That kitten really was cute. All golden fluff and big blue eyes. Adorable."

Castle widened his own big blue eyes in the hope of being thought adorable, and sneaked a little closer. "Now I'm here, can I do anything for you? Make you coffee, or lunch, or get your shopping?"

"Coffee would be nice, but I" –

"I'll do it. Just tell me where to find everything."

Under Beckett's brisk instructions, Castle prepared coffee and set it down in an easy-to-reach location.

"There," he pointed out. "Easy."

"Thanks."

She shivered. Castle, not a man to ignore small movements, noted not only the shiver but the following wince. "Hurts?"

"Mm."

"You need a hot water bottle, or a heat pad. Or," he said smoothly, and shifted right up close, "me." He placed his arm around her shoulders, not pressing, and rearranged his body so that without moving she was enclosed in his warmth.

"Uh?" she managed.

"I'm nice and warm. Just let me warm you up." He had nearly said _heat you up_ , but if he wasn't dead yet he wasn't going to push his luck. He handed her the coffee mug, and kept the conversation light – and a long way away from _you feel so good against me_ or _why are you not killing me already_ or even _why don't I take you back to mine where I can look after you properly?_ , none of which would improve the moment. Beckett stayed quite still and calm in his light clasp, her feet tucked under her as she had been at his, and then quite unexpectedly leant her head on his shoulder. The flick of her hair on his neck reminded him irresistibly of Onyx.

"Onyx does that," he blurted out.

"Uh?"

"Tucks her head into my shoulder, just like you did then." Beckett sat up, and huffed out a pain-soaked breath. "Come back," Castle suggested, and encouraged her to do so by very carefully pressing her upper arm. Amazingly, Beckett returned to her semi-snuggle.

"I am not your cat," she snipped. "Didn't we have that conversation already?"

"I _know_ you're not a cat, Beckett," Castle said patiently. "If you were my cat you'd be curled up in my lap and purring at me, or sprawled over my chest and shoulder. I mean, you could do both of those things and I wouldn't mind a bit, but" –

"Shut up," –

"but you're not a cat. I'd have brought her, but she wandered off again."

His hand slid up and down Beckett's bruised arm, trying to warm her. Castle abruptly noticed that he was petting Beckett exactly like he petted Onyx, but since it was working – or Beckett wasn't objecting – he decided to stick with it till he was told to stop. It was beautifully peaceful with her head on his shoulder, and while comparing Beckett to his cat hadn't been the best idea he could have had, the longer her head stays there the more the resemblance catches at his mind. He thought, happily, that the best of all possible situations would be Beckett's beautiful head tucked into his chest, over his heart; and his beautiful cat close by. Fortunately, he managed not to articulate that thought before he realised that it would all be rather crowded, and instead drained his coffee. His watch told him that he'd been here for most of an hour, in which they had done almost nothing, barely talked, and somehow had found quiet, comfortable peace, Beckett curled into him, which, he eventually worked out, was because she had fallen asleep.

* * *

 _Thank you to all readers and reviewers on this and on Modern Metrosexual (which I should have said is set to the tune of Tom Lehrer's Elements Song, but since I totally failed to make that connection till one of you pointed it out, I couldn't. Even though I know both.)._

 _You will be pleased to know that there is no accompanying insanity for this chapter._


	5. Chapter 5

**Chapter 5.**

Moving Beckett seemed like a very bad idea. She was clearly still in considerable discomfort, and anything he could have done would undoubtedly flick some very painful switch. Reluctantly, Castle stroked down her hair, and then patted her cheek – an area which was not bruised – tapping until her eyes opened and he received a sleepy glare.

"You fell asleep on me. You'll be stiff and uncomfortable if you stay like that."

Her eyes were hazy and soft. She tongued her lips, then uncertainly nipped her lower lip. Castle failed entirely to resist his own urges, and gently gathered her into a soft, unpressured embrace, dropped a delicate buss on the tip of her nose, and then placed another delicate, gentle touch on her mouth. He lifted off, shocked by the sensation that raced through him when he kissed her, almost overwhelmed by the need to repeat it, to go deeper: to explore and taste and finally conquer; but her injuries were an effective barrier.

Beckett sat stock still, silent and, Castle thought, as shocked as he was. He expected – he didn't know what to expect: shooting, or slapping, or imprecations. Instead, she leaned forward cautiously and kissed his cheek, as light as the brush of Onyx's tail.

"I think…" she started.

"I think maybe I'd better go home," Castle stammered. He watched a flash of regret flicker through Beckett's eyes, turning them more green than hazel, oddly enlarged irises, gone upon the thought. Simply an illusion from the way in which the light fell.

"Yeah… um… if you wanted you could come by tomorrow? Keep me company while I'm not allowed at work?"

"Sure. Absolutely. Can I bring anything? Food, drink, games, movies? Can I bring Onyx too?"

"I've got plenty of food, drink and movies. You can bring your cat, if you can find her."

It didn't occur to Castle that Beckett's comment of _if you can find her_ was very peculiar until long after he was home, indulging himself in a glass of excellent Rioja after dinner and with Onyx on his lap, still not her normal elegantly sinuous shimmer of darkness, but clearly improving. She'd perked up mightily when he gave her the small amount of coffee he thought would please her, and she was listening to his account of the day with, Castle flattered himself, considerable attention.

"I was a bit surprised she let me in," he related. "Beckett's not known for her love of company when she's sick – I told you that. But she let me make her coffee – she practically swims in the stuff – and then she didn't object when I put an arm round her." He gently rubbed under the cat's chin, and she purred happily at him. "She even cuddled in and leaned on my shoulder. It was a lot like you, really." The cat emitted a questioning miaow. "Soft hair, snuggly, happy to be petted very carefully. She's still badly hurt, but it's getting better." Onyx settled back down again, as Castle played with her swaying tail.

"But the absolute best bit was that I kissed her." The cat stared curiously at him. "I didn't mean to. She's injured. But she bit her lip and she's just so sexy when she does that and she was all soft and not really quite badass Beckett at all and she's irresistible. I could have stayed there kissing her all day, but I couldn't. She's injured," he told the cat again. "But it was amazing. I've never felt that before. It was electric. Everything I dreamed it would be. Even more amazing, she _liked_ it. She even kissed me on the cheek. I'd have preferred on the lips, but I suppose that wouldn't have been such a good idea. I don't think serious kissing's good for injuries."

He hummed softly, and stroked Onyx some more. "I really think we're getting somewhere. I really do." Onyx mewed at him. "Good, you agree. She said I could go round tomorrow, too. I can take you." He stopped. "That was weird," he said. "Why'd Beckett say _if you can find her_? That's an odd thing to say. How'd she know that you do this amazing disappearing act?" Naturally, answer came there none. "I must have told her that you sneak off and can't be found." Onyx stood up, turned round, and clambered on to his shoulder. It distracted Castle immediately. "You must be a lot better," he told her happily. "Good." He ruffled her fur, and she butted her head into his neck. "I'm really glad you turned up in that alley. I never knew what I was missing."

The following day, Onyx was back to her usual trick of hiding. Castle, more than a little disappointed that he couldn't take her to Beckett's apartment, loaded himself up with ice-cream and Beckett's favourite Thai food, and arrived there shortly before lunchtime to unusual acclaim.

"But Onyx wasn't there when I looked for her," he said as they finished lunch. "I thought bringing her would amuse you. She glares at me just like you do."

Beckett snickers. "All cats glare. I think they hand it down the generations. You know, along with how to be adorable as a kitten, and then how to train your human as they grow up. You seem to be pretty well trained already."

"I'm perfectly house-trained," Castle pointed out smoothly. "I can cook, tidy up, and do my own washing, all while looking after my mother and daughter."

"A modern-day saint," Beckett jibed gently.

"Not quite," Castle murmured, and slid across the couch to catch her. "See, when I'm with you, I don't feel saintly at all," and he bent his head to kiss her, just as gently as the day before.

It started out gently. If only Beckett hadn't parted those satin-soft lips, it might even have stayed gentle. But she did, and Castle was anything but proof against the open invitation. He did remember not to squeeze her, but with his hand slipping into her hair, his tongue exploring carefully, and her whole demeanour relaxed and easy against his arm, the kiss became deeper, harder, and far more passionate than might have been wise.

He only managed to lift off and let go because his hand slipped down her arm and she flinched as it touched the ghastly bruising.

"I'm sorry," he forced out. "I shouldn't have… I didn't mean to hurt you."

"That's okay," she said tightly, pain creasing her face.

"No, it's not okay. You're still injured. You're not supposed to…" he couldn't think of a good way to finish that sentence. "Look, I better go." He scrambled into his coat, under her gaze. "I'm sorry," he said again, uselessly.

As the door closed, he thought he heard "Don't be," but by the time that registered he had shut the door, and he wasn't brave enough to go back.

Castle took the long route home. The really long route, that circled past a small park, a coffee bar where he stopped and downed a double espresso, a grocery store where he restocked with luxury cat food and treats. None of it alleviated his misery at all, but it wasted almost two hours. The only thought his mind would hold was _what a jerk you are, mauling Beckett while she was injured_. _Couldn't you have waited?_

He went straight to his bedroom to drop on to his bed, but to his astonishment Onyx was already there, curled up in the centre of her pillow. She opened one emerald eye as he lay down, propped up on his own pillows, and then walked primly on to his chest, nudging at his chin. He responded by cuddling her in, and simply stopped. She mewed at him, and nudged some more, and then batted a paw at him. He caught it, gently.

"I'm not really in the mood to play. I think I really screwed up. I shouldn't have kissed her again. She's _injured_ , dammit! But she's just so beautiful and I can't keep away from her and I've been in love with her for months and months and… oh, hell, I've so totally messed this up." Onyx patted her paw at his cheek, and nuzzled him. He petted her, and she purred at him, arching into his careful hands. "I don't know what to do. I thought she was enjoying it too but then she flinched and …oh, fuck, what a mess."

The cat purred. "You're simple. I stroke you and you purr. Nothing complicated. People are a lot more difficult. I just wish I knew what Beckett was thinking. I mean, whether she likes me or not. She let me kiss her but then she's injured and I hate the thought that maybe she just let me because she couldn't push me away." He winced, ashamed and unhappy. He had never, ever, gone where he wasn't wanted and invited.

Onyx batted his face with her paw, left it on his cheek, and delicately extruded her claws until they were just pricking his skin.

"Don't you start," Castle said miserably. "I don't need you getting upset with me too." Her claws retracted, and the paw returned to his chest. "What'm I gonna do, Onyx?" She simply purred, deep in her chest, more of a vibration than a sound, and settled down over his bleeding heart.

Eventually he had to get up, and soothed his scarified self by starting on preparations for dinner. Part way through, he noticed Onyx sitting at the outer door. "You want to go out?" he asked her. "After you got so badly hurt?" She fixed him with her flat, feline stare. "Okay. But be careful, and be back by bedtime," he told her ridiculously, and opened the door. She prowled out, without looking back.

Castle didn't feel talkative over dinner, but since his mother was voluble on the inadequacies of the director of her latest attempt at hitting the big time again, and Alexis was bemoaning the loss of two marks on her biology test (which had made not one iota of difference to her straight-A average since it had been the _only_ two marks she had lost), all he had to do was maintain a suitably sympathetic expression and occasionally emit some suitably sympathetic words.

"Where's your cat?" his mother suddenly asked.

"She went out," Castle replied, not inviting more conversation. "She'll be back later."

Later, however, she still hadn't reappeared. It was long past the hour at which she'd usually arrived, and Castle had had a fortifying Scotch to try to relieve the nagging feeling that he'd not just messed up with Beckett, but that his beautiful cat had also abandoned him. He picked up his phone, and discovered that Beckett had texted him. He opened it with trepidation.

 _I liked it. Save your sorries for an actual screw-up._

He was still staring at it when Onyx strutted proudly through the study door and leapt into his lap, climbing on to his shoulder. She was damp, and when he looked out the window the rain was lashing down. He found a towel to dry her off, and then replaced her on his chest.

"Look," he said to her, and showed her the text as if she could read it. "I _didn't_ mess up. She's okay with me." He enveloped the cat in his arms. "It's as if she read my mind."

He took himself off to bed completely eased and relieved, snuggled down, and drifted towards sleep with Onyx's soft purr in his ear. On the edge of true slumber, half-dreaming, he wondered where Onyx had been, and how she was sneaking in and out without him noticing. Closer to Morpheus, he mistook his cat's soft fur for the feel of Beckett's equally soft hair, and reached out, only to realise his mistake. Tomorrow, he mumbled, tomorrow he'll introduce them.

But the next day Onyx had worked her feline sorcery and disappeared again, which meant that when Beckett arrived at his door, bearing not flowers but a DVD of Forbidden Planet and creaking rather worryingly, he had to admit that she'd slunk off.

"You know, if you hadn't showed me the photos I wouldn't believe this cat exists. I've never seen her."

"Of course she exists," Castle squawked indignantly. "Why would I make up a cat, or the vet bills?"

"You keep telling me about your excellent imagination," Beckett said provocatively. "Come on, you have to admit it's a weird tale. Pure black pedigree cat appears from nowhere in an alley just when you're taking a break? No owner, no chip. Weirdest of all, it's instantly attracted to you and you said you fell in love with it immediately. But somehow it's never here when you want to show me it."

"She. Onyx is a girl."

"Okay, her."

"The boys have met her. They'll tell you she's real."

"Forgot that. Okay, she's real. It's still deeply suspicious that she's never around when I want to meet her. I think you don't want me to meet her."

"What? Who are you and where is the real Kate Beckett? It's my job to come up with conspiracy theories and alien invasions. Why wouldn't I want you to meet my cat?"

Beckett shrugged. "Just a thought."

"Anyway, I think you'd get on with her brilliantly. Same cool stare, same elegant looks" – Beckett spluttered into her coffee – "she even likes coffee."

"She _what_ now?"

"She drinks coffee. Well, a few drips. I'm sure caffeine isn't good for cats."

"You give her coffee?" Beckett repeated, stunned. "You're… you're _insane_. I suppose next thing you'll tell me that she reads your books."

"Don't be silly. But she does like watching the screen when I type."

Beckett shook her head sadly at his folly. "You have got it bad, Castle. You really have."

He pouted at her. "She's gorgeous. She sits in my lap or perches on my chest and she's infinitely strokable. She even sleeps on my pillow. I just wish she were here to meet you. She never seems to be around when you are."

"Put the movie on," Beckett said briskly. "It'll stop you moping about your cat's social life."

Castle complied. "Are you feeling better," he inquired, just before pressing _Play_.

"Yeah. Still covered in bruises, but getting there. As long as I'm careful, I'm fine."

"Same as Onyx," he replied, and then stopped dead.

"Aren't you going to start the movie?" Beckett prodded.

"Yeah, sure." He pressed _Play_ , and the intro began to roll. Castle didn't pay it a single bit of attention. He must have had a brain-boggle. He'd gone insane. It was quite impossible, even for him to believe. It was so way out it was practically coming in the front door again. No matter the breadth of his mind – which would span the Pacific, most days of the week – he simply could not encompass the concept that had just fallen into his head. There was absolutely _no way_ that Onyx the cat could be a shape-shifted Kate Beckett.

And yet his boggled mind wouldn't leave it alone. They're never in the same place at the same time. Their similar expressions, and Onyx's attention to his reading, his writing, and her love of coffee. Cats were not notable coffee drinkers. And the unexplainable coincidence that they had both been beaten up on the same day. Even Onyx's disappearances. But against that, Castle really didn't think that Kate Beckett, shape-shifted or not, would snuggle affectionately against him and let him pet and stroke her.

Except that she just had, only yesterday: she'd let him kiss her and even sent him a reassuring text – _after_ he'd poured out his heart to his cat. She'd accepted an invitation to dinner and then the theatre – _after_ he'd told Onyx how he felt about her. She'd had a sore back – straight after he'd had Onyx chipped and got her given her shots.

This was insane. Even for Castle, professional believer-in and imaginer of almost anything, no matter how strange, he could not get his head round the concept that there were really, truly, actually and in fact such things as shape-shifters. In Manhattan, no less. It was all an enormous set of coincidences, and he would prove it by getting Onyx and Beckett in the same room at the same time. Whatever he might theorise to annoy Beckett, when it came to cold, hard reality, he baulked.

He returned his attention to the film, and found that, amazingly, only a few minutes had passed. It wasn't much of a loss, since he could recite most of the dialogue without effort. From Beckett's rapt attention, and the movements of her mouth, she could do so too.

Castle nudged himself across the couch to Beckett's curled-up self. (Even her posture reminded him of the cat. He was going insane. Definitely.) If she had liked kisses – and she'd said so, in writing – then she would like it if he put an arm round her while they watched the film. He insinuated an arm around her slim shoulders, and not only did she nestle in, she leant her head back on his shoulder and dropped a hand over his knee. The charge ran right through him, and without any conscious thought on his part at all his arm round her shoulder dropped down to leave his hand on her hip and she as close as she could be without sitting in his lap in the first place.

"Beckett?" he murmured questioningly.

"You're comfy," she mumbled back. "Nice and warm and cosy." She wriggled, presumably to become perfectly comfortable, and for a second Castle thought that her movement was just like Onyx's boneless wiggle. He shook the thought from his brain. Shape shifters are _not real_. ( _But it would be so cool,_ another part of his undisciplined mind whispered. _Just so amazingly cool_.)

His undisciplined mind landed on a much better idea than idiotic theories about shape-shifters (and anyway Beckett should shift into a black panther, or a Bengal tiger, not a mere domestic cat no matter how gorgeous, to go with her badass personality). He slipped a finger under Beckett's chin, and lifted her face to his so that he could plant a light, teasing kiss on her lips. Even before their mouths met, she made a small, contented noise, almost a purr – _no_! That was ridiculous. Beckett didn't purr. Growl, sure. Every time he messed up or annoyed her or she was irritated, but she did not purr.

She did kiss, though. Oh boy oh boy oh boy, did she kiss. Light and teasing? Only for a microsecond, and then her lips opened and she licked along the seam of his and invaded. She didn't ask, she demanded (just like Onyx) his attention, and she certainly had it. All of it. The white heat of their merged mouths was inescapable; the sparks running over his skin undeniable; and the way in which she was kissing him: passionate and open and scorchingly hot; made it clear that she was as into it as he could ever have hoped or dreamed.

He couldn't do more than kiss her: couldn't press her into him or hoist her into his lap or (but he wanted to, oh, _how_ he wanted to) take her to his bed; but he could show her just how much he felt for her, just how much he wanted her, simply through his lips and tongue and mouth on hers. She was equally restrained: possibly still cautious of her bruised body, her hand on his shoulder but not exploring further, his remaining at her hip. The pressure of her hand burned into him, but he couldn't reciprocate. Not yet.

He tore himself away from the addiction of her mouth. "You're amazing," he husked. "I never thought…"

"Didn't you?" Beckett said, quirking an eyebrow at him. "I got the impression you thought about it a lot."

"Well, yeah, but, well, I never thought it would be like that and I never thought you would and I'd pretty much given up on it," Castle rushed out in one brain-dumped, open-mouth-and-insert-both-feet spill of words.

Beckett smiled, calm and remarkably collected. "Guess you were wrong, then. Close your mouth, Castle, you'll catch flies," she added.

"If you weren't still bruised to bits, I'd get you back for that," Castle rasped.

"If I weren't still bruised to bits, I might let you," Beckett flipped back, leaving Castle speechless once more. "But since I am, and the movie's done, I think I'd better go home and have another hot bath." Castle gleeped, not quite far enough under his breath, at the instant vision. ( _See_ , his more sensible side pointed out, _she has baths. Cats don't like water._ ) "Mind out the gutter, Castle."

"It's not in the gutter," he oozed. "It's in a bath."

She growled, and applied sharp nails to his ear.

"Ow! I think I'll stick with Onyx. She doesn't claw me."

"That's because you don't make dirty suggestions to her."

"Of course not! She's a cat. Ugh. I need to scrub my brain now."

Beckett sniggered nastily. "You're so easy, Castle."

"And you're so mean. If you were a cat you'd be playing with your prey."

"Just as well I'm not, then." For an instant, Castle thought that her eyes had gone that odd, large-irised green once more. It must have been a trick of the light, because they were perfectly normal when he looked again. She stood up, only wincing a little, and looked around for her coat.

"Here it is." He held it for her, waited as she slid her arms in, and then settled it on her frame. "Till tomorrow, Beckett."

"I'll be in. Your choice of movie."

Castle escorted her to the door, and before opening it took full advantage of his height and size to clasp Beckett back in again, very gently, and kiss her, not gently at all.

"Night, Castle," she said, and there was an undercurrent to her voice that made him think she'd rather have stayed.

* * *

 _Thank you to all readers and reviewers._

 _Tomorrow is the final chapter. All shall be revealed._


	6. Chapter 6

**Chapter 6.**

Onyx turned up at dinner time, and amused herself by winding in and out of Castle's legs as he prepared and then ate his dinner.

"She's not interested in anyone else, is she?" Alexis asked rhetorically.

"It's my charm and ruggedly handsome looks," Castle replied, to a groan from Alexis, a huff from his mother, and a loudly derisive miaow from the cat.

"It certainly isn't your modesty, kiddo."

"And on that flattering note, I shall make my exit."

Castle repaired to his study, not pursued by a bear but preceded by Onyx, who appeared from under the dinner table and led him out.

"I had the dumbest idea today. For a moment, I thought that you were Beckett in disguise. I mean, _obviously_ that's nonsense, because shape-shifters don't exist, but it would be so _cool_ if they did. It would explain a lot about you, too. How you're never there when Beckett comes by, and how she's hurt just the same as you. I know it's just a coincidence, but it would be _amazing_. Anyway, I'm going to prove it isn't true by getting you two in the same room." He drooped. "It would be great, though. Really great. Though if shape-shifters were even a thing I'd have bet on Beckett being a much bigger cat. A black panther, like Bagheera out of the Jungle Book. Or maybe a tiger, or a leopard. Something lethal, anyway."

Onyx favoured him with a flat-eyed, sardonic stare that somehow made it perfectly clear that she thought him utterly insane.

"I know. I'm being silly. Come here, then." She jumped up into his arms. He tickled her under the chin, and she purred softly, growing louder as he stroked her more firmly. "You're almost mended," he murmured to her. "Good. Don't do that again. One of you putting yourself in harm's way all the time is quite enough for me. It's not good for my blood pressure. You need to take care. God knows Beckett doesn't. I get that it's her job, and I wouldn't want it any other way, but it's scary." Onyx miaowed, and pushed her head into his shoulder. Castle flirted with her ears, pondering. "It's still weird," he said into the quiet study. "So many coincidences."

He pulled the laptop towards him, making sure that Onyx could see the screen too. "Let's have a look," he told her. "You can find anything on the net. Someone will suggest a way to detect a shape-shifter."

An hour or so later, he had found dozens of ways to detect a shape-shifter, accompanied by Onyx's contemptuous feline stare. Clearly she did not believe in such tales. Reading them through, Castle was inclined to agree. One suggested a decoction of mandrake, silver, quicksilver and spider-webs, spiders optional. He shuddered. Another sure-fire detection method involved DNA testing, which Castle was certain would work, if only he knew anyone who wouldn't laugh him out of state for trying it. Besides which, Beckett must have had blood tests before. Alternatively, he could feed the suspected shape-shifter ibuprofen, but that webpage noted that if the animal was normal, it would die in agony. _Not_ a good option _at all_. On the other hand, Beckett had been swallowing Advil like there was no tomorrow, so that didn't _prevent_ her being a shape-shifter.

None of the internet theories were plausible, practical or performable. Castle scowled blackly at the screen. "That's no good," he grumbled at Onyx. "How'm I supposed to prove that you aren't Beckett?" Onyx merely yawned, showing a full set of sharp white teeth, and resettled herself comfortably on Castle's chest, where, except for a short break to drink her evening drops of coffee and visit the bathroom, she stayed, purring quietly.

* * *

Castle didn't know what small noise woke him in the very early hours of the morning, but wake he did. Onyx wasn't at his neck, either. He sat up, rubbing his eyes, to see if he could spot her, but she wasn't anywhere in sight. He sleepily staggered out of his room to the study, where she was also nowhere to be found, and then to the main room. He was just in time to see the handle turning to close the outer door without a sound. He flung himself across the room, but his frantic glances around the dark hallway didn't show him anything. He checked everything in case it was a burglar, but nothing was missing at all: his wallet and laptop exactly where he had left them. He was almost ready to tell himself he'd imagined it: too much writing or an over-active imagination, but then he had an idea. A completely and utterly insane idea, but an idea. He grabbed his phone and called Beckett.

There was no answer. Which _of course_ wasn't determinative, but he happened to know that Beckett never, ever had her phone on silent even when off-duty – she'd said once, in a moment of abnormal confidence, that it was for her father – and so her not answering was certainly _highly_ suggestive. Without any further ado, he dressed, grabbed phone and wallet and slipped out of the loft as silently as… well, as whoever had left moments ago.

"Where are you off to, Mr Castle?" the night doorman asked.

Castle stopped. "Did you see my cat go by?"

"No, but I wasn't looking."

"Anyone else?"

"Not a soul."

Okay, so if Beckett was Onyx or vice versa she certainly hadn't gone out as her Beckett-self. Castle waved a brief farewell at the doorman, hailed the first cab he saw and directed it to Beckett's apartment, as fast as it could manage. His, _still_ completely insane, thought process could vaguely be described as _if I get a cab I can get there faster than a cat or than Beckett. She'd have to shift back to Beckett and then get a cab, which gives me a few minutes on her._ Swiftly followed by: _This is insane._ But he had to know.

The cab deposited him at Beckett's unmanned door, and Castle went up, quietly in deference to the hour. He rang her bell, waited, rang it again, waited, rang it a third time. There was no answer. Again, not determinative, but highly suggestive. He stood in the dark hallway, stalking a solution to the concatenation of coincidences – and hoping that Beckett wouldn't shoot him when he found that he was wrong. He didn't think that she'd exactly appreciate his latest theory.

He didn't have to wait long for something to happen. The door to the stairwell opened a crack and, under Castle's astonished, disbelieving eyes, Onyx prowled out, stopped, sniffed the air, and abruptly started to retreat. Castle moved like lightning to catch her before she dissolved back into the dark.

"What are you doing here?" he asked her, silkily interrogative. "More to the point, how did you get out? Last I knew, cats couldn't manage door handles. Not mine, anyway." He picked her up. "I thought it was all a coincidence, but it wasn't, was it – Beckett." The cat spat at him, and hissed angrily. "You wouldn't know how to come here unless you lived here, and if Beckett had had a cat – you – she'd have taken you back as soon as I showed her the photos." He deftly avoided the cat's infuriated swipe, and took a firm hold of her front paws. "How'd you do it?"

The cat wriggled frantically, twisted in his grip, and managed to jump down, yowling when she landed, as if the movement had hurt. Castle took advantage of her moment of pain and collected her again, ensuring that she couldn't swipe at his face. She squirmed and wriggled and twisted and hissed and clawed and spat, and made no impression on Castle at all. Eventually, she simply glared viciously, ears laid flat to her head, tail whipping furiously.

"Stop running away, _whoever_ you are." Castle sat down with his back to Beckett's door, and then turned round to realise that he was leaning against a very discreet and indeed almost undetectable cat flap. "Ohhh," he breathed. "That's suggestive. Why would Beckett need a cat flap when she hasn't got a cat? She – you – _told_ me she didn't have a cat. It's for you, isn't it? So you can get back in without anyone noticing."

The cat continued to glare, with an air of caught-out disgruntlement creeping into its look.

"C'mon. I've worked it out now. You might as well admit it. Besides, this is so _cool_. I can't believe you really exist. It's amazing. Fabulous. Fantastic."

The cat's expression altered to a very familiar look of resigned irritation, and its ears came up to a less angry elevation.

"If I let go, will you open the door?" he asked persuasively. "I think we've got a lot to talk about." He stroked her gently. "A _lot_ to talk about," he repeated.

Onyx-Beckett gazed up at him, clearly assessing his sincerity, and then suddenly clambered into her as-a-feline-accustomed position on his shoulder, butting her head into his neck in a familiar and comforting way. He petted her just as he always had when she'd balanced there, and was hugely relieved to hear her purr.

"Okay then, deal." He let go of her. She slithered through the cat flap as he waited nervously, not yet sure she'd hold up her end of the bargain. He faintly heard a soft sigh, and then the lock turned over and the door opened, Beckett, fully dressed in soft cotton tee and pants, behind it. Castle stepped inside and instinctively simply pulled her into his arms. His head dropped to hers, foreheads touching, and he stood there for a moment, only holding her, until he stroked gently up and down her back, and she arched into his hand in that same boneless, feline way as Onyx had and – he was quite definite about it – purred in pleasure.

"I've got you," he said comfortingly. "Whoever you are, I've got you and I am _keeping_ you." He tipped her chin up, and kissed her: sure, searching and utterly sensual. Her arms slipped round his neck, softer hands than he would ever have expected if he didn't know that sometimes they were paws; the tips of her nails reminding him that sometimes they were claws. He kissed her again, deeper, softer, slower; taking time to explore, to sense her curving and melting against his broad chest, to ease her before the conversation they had to have; but also simply for the sheer joy of kissing her as he had wanted to, right from the very start.

Finally, he drew his mouth away and drew his Beckett after him to the couch; brought her down into his lap where she had spent so much of the last week, and wrapped his arms around her. He meant to ask _why_ , but his mouth opened on, "How? How do you do that?"

Beckett shrugged. "It just is."

"That's not a story, Beckett! You can't tell me that. It's no fun. Not cool at all." He was practically bouncing with the joy of finding out that legends – or that particular legend – came true. "C'mon. There's gotta be more to it than that." He grinned widely at her, as delighted as a small child on Christmas morning. "Will you show me? Please?"

Beckett groaned. "There's a _reason_ I keep this a secret."

"But I've worked it out. Pleeeeaaassseee?" He opened his eyes to their very widest, pleading with her. Beckett emitted a noise that resembled a hiss. "Pleeeaaaseee?"

"Stop whining."

There was no warning, no messy, gruesome, painful writhing, no gloopy fluid, no cracking of bone or tortured noise. One instant Beckett was sitting on his lap, the next she'd been replaced by Onyx. The only indication of anything happening had been a slight sighing noise.

"Wow. Wow wow wow. That's incredible." Onyx-Beckett hissed derisively. "No, really. Can you come back again straight away?"

Another sigh, and Beckett was back on his knee. "Where do your clothes go?"

"Trust you to think about that," she muttered. "I don't know. It only works for natural fibres, though."

"Aren't you _interested_?" Castle was horrified at her lack of concern or curiosity.

"I was _interested_ in keeping it a secret."

"Hm," Castle hummed very sceptically indeed. "Were you?"

"Yes!"

"I think you're fibbing," he teased. "You had to know I'd work it out eventually."

"Didn't," she said sulkily, and gave him Onyx's flat, annoyed stare. "I didn't think even you would believe something that way out. You're insane, you know that?"

"I just have a very wide definition of reality. I'm quite capable of stripping away all the extraneous camouflage and believing that what remains is the truth. However unlikely."

She slumped. "Now what?"

Castle didn't like her slumping, especially since it wasn't into him. He tucked her Beckett-form against his body, and her head on his shoulder. "I wasn't planning on telling anyone, if that's what you're worried about. And since you know exactly how I feel – actually, let's just talk about that. You _spied_ on me," he growled. "You cheated."

"Cats are curious," Beckett said airily.

"Curiosity killed the cat."

"And satisfaction brought it back," she capped his line, and smirked wickedly.

"Is that so?" Castle asked, in a slow, conversational drawl. "Guess I know what I need to do, then." A fine line of colour rose along Beckett's face. "You're distracting me. You sneaked into my bed, and you snuggled up to me, and I told you all my secrets."

"It's not my fault that you never stop talking. Who talks to their cat anyway?"

"Everyone." He stopped to regroup. That was as might be, but it wasn't what he really wanted to know _right now_. "So why _exactly_ were you-as-Onyx stalking down an alleyway behind where I was giving a reading?"

Beckett remained absolutely silent for a moment, and then, as she failed to find any sort of an answer that she wanted to give, turned back into Onyx.

"That is _not fair_!" Castle squawked. "You can't do that." Onyx sat and coolly washed a paw. His imprecations went past her without a pause. "Are you going to do that every time you don't want to talk? Because if you are, I'm going to start asking questions in the precinct. Or Remy's. Or the middle of Central Park. You can't pull that trick there."

Onyx washed the other paw, simply, Castle thought, to prove her indifference, and then became Beckett again. "That's not fair," she said crossly.

"And you changing into a cat and _not telling me_ is?"

"Yep. Anyway, you _chipped_ me," she said with high indignation. "And how was I supposed to get that out when you put in a cat flap _tuned_ to it? Or explain how I had a cat's microchip in my back in the first place?"

"I didn't want you stolen. And I still want to know what you were doing in that alley."

Beckett's high colour ramped up another five notches.

"You were looking for me!" Castle suddenly said. "You _wanted_ me to pick you up and take you home. You were – you were finding out if I was genuinely interested. Why, Beckett, you're a romantic at heart. You like petting and snuggling."

"I'm a freaking _cat_ , Castle. All cats like petting and snuggling."

"Good," he said suavely. "I like petting you. Cat or not." He demonstrated, stroking a warm hand from the top of her head down over her hair, then down her back all the way to the dimple at its base. She curved into it. "And you like _me_ petting you." His palm wandered round over her hip to find her thigh. "I'm sure we can find a lot of time for petting." It slid back to her hip, and his fingers explored the edge of her soft pants. Shortly, her tee lifted slightly, and his hand curled on to bare skin, as soft as the fur it had been only a moment before.

When she sighed, it had nothing to do with shifting form, and everything to do with the way he kissed her: as if they had all the time in the world and yet none to spare; as if she was (oh, she surely was) the whole of his world. His hands moved on her as if they knew every inch of her body, and yet in this form he had never touched her with intent. The tee rose higher, and still higher, his hands following, and she turned into him and gave herself up to his wickedly searching mouth and arousing touch, the purr rising in her throat. He came away from her mouth, forcing a disappointed little mew and a warning brush of nails under the shoulders of his button-down; but it soon changed to a soft, vibrating moan when he took liberties with his mouth instead, played and lipped and licked and sucked until her nails dug in and she clung to him.

"Take me to bed," she purred seductively. "After all, I've spent plenty of time in yours."

"Come here, then," Castle rasped, stood, and swept her up. "You don't need to be a cat for me to carry you to bed." She curved into his body and slung arms around his neck, and the bedroom door swung closed behind them.

"Will you still be Beckett in the morning?" he asked, much later.

"Whoever you like," she replied, and tucked her head into his neck and her arm across him.

* * *

A few weeks later, Castle's intense curiosity about everything to do with Beckett's two-natured self had largely been satisfied, although almost every night she had threatened to shoot him if he didn't stop asking questions. She seemed to be a complete one-off. Much to his disappointment, there was no shape-shifting community in the underworld of New York; her father did not become a cat, as far as she knew her mother had never become a cat, she knew no-one else who was anything other than human. Not even the massive Detective O'Leary at Central Park precinct, Beckett's long-time pal, who Castle had really, really hoped was secretly a grizzly bear, was anything other than utterly normal. As far as Beckett knew, she was unique. (In _so_ many ways, Castle thought.)

"But what about blood tests?" Castle asked plaintively, munching the Hallowe'en candy that he'd brought round to Beckett's apartment in honour of the date, and admiring the timing of the full moon lighting the Manhattan sky. That full moon was just the last gloss to make up a truly excellent All Hallows Eve.

"Nothing out of the ordinary. Cat shows cat, human shows human. Same for DNA." He drooped, again.

"I wanna know how it _happened_ ," he said.

"Must have been sorcery." He perked up, in the hope of an answer. She had brushed that question off every time he'd asked. "Just leave it, okay?"

"Hmph," he sulked. "You'd think you'd tell me. Hallowe'en gift. C'mon. Sharing the secret by the light of the full moon?"

"You wanna share the secret? Hmm. I know how to take your mind off it for now." She stretched, rubbed over him, and stalked to her bedroom. Castle didn't loiter on the way.

He was sprawled out across her bed with his eyes shut, after another round of intense and spectacular lovemaking, waiting for Beckett to return from her clean up and to nestle in, choosing whichever form she felt like, when there was an odd noise.

He peeled his eyes open into the cold, bright moonlight and sat up with a shriek. Prowling towards him was a full-sized, coal-black, evidently female jaguar, green eyes bright and mouth open with _very_ sharp teeth on display. She padded to the bed, and leapt up, pinning him down with broad, heavy paws on his shoulders. Hot breath gusted past his ear. Claws pierced the sheet beneath his shoulders.

"Beckett? Beckett? Please tell me you're Beckett? This isn't funny, Beckett! BECKETT!"

The jaguar emitted a coughing laugh and bent her head to his neck, sharp teeth against his skin, not quite drawing blood. _Yet_ , thought Castle's terrified mind, body paralysed in fear.

"Curiosity killed the cat," she said, perfectly clearly through the open jaws around his neck, "but satisfaction will bring you back."

* * *

 _ **One year later:**_

 _ **Newspaper editorial, October 31**_ _ **st**_ _ **2010**_

 _Rumours of a pair of big cats, possibly black jaguars (_ panthera onca _), continue to swirl around Manhattan, as more and more people report sightings. Despite extensive searching for a year, ever since the rumours began, no evidence at all has been found to prove that these beasts exist. We think folks have gotten a bit carried away with the Halloween (or alcoholic) spirit._

Beckett put the paper down and smiled at Castle over the breakfast table. "Or maybe they didn't."

 _ **Fin.**_

* * *

 _Happy Hallowe'en, everyone! "From ghoulies_ _and_ _ghosties and long-leggedy beasties, and things that go bump in the night - good Lord, deliver us."_

 _Thank you to all readers and reviewers who have prowled along this piece of silliness with me. Thank you especially to guests, whom I cannot thank directly._

 _All being well, I intend to resume What's in a Name next week._


End file.
